In the practice of diagnostic medicine, it is often necessary or desirable to perform a biopsy, or to sample selected tissue from a living patient for medical evaluation. Cytological and histological studies of the biopsy sample can then be performed as an aid to the diagnosis and treatment of disease. Biopsies can be useful in diagnosing and treating various forms of cancer, as well as other diseases in which a localized area of affected tissue can be identified.
During the biopsy procedure, care is taken to minimize the physical trauma inflicted upon the intervening tissues that surround the affected area or target tissue and at the same time to protect the practitioner from health hazards. One typical biopsy procedure includes inserting a hollow biopsy needle through the intervening tissue into the target tissue to be sampled. The sample tissue is then harvested through the needle by applying suction through the needle, typically with a syringe.
Special considerations apply if the biopsy is to be performed on an internal organ deep within the body such as the liver. Previously, obtaining a tissue sample from an internal organ, such as the liver, was carried out percutaneously by entering the skin in the vicinity of the organ and thereafter extracting a core of liver material through the biopsy needle. This method, although effective in obtaining an adequate amount of tissue from the liver, is no longer acceptable practice, since it is not uncommon for the patient to suffer from serious health complications caused by the biopsy. For example, patients generally experience extreme pain, and additionally, the liver profusely bleeds after percutaneous biopsy. Moreover, liver biopsies are typically performed on patients having liver disease, liver transplants and coagulation disorders, and such conditions further complicate percutaneous liver biopsies.
Alternatively, tissue samples may be obtained without the problems associated with percutaneous biopsy by accessing the liver via a transjugular procedure. Known techniques involve accessing the liver through the jugular vein with an elongated biopsy device. Typically, these biopsy devices are identical to typical single and double action biopsy devices except that the inner and outer needles are elongated to access the liver from the jugular vein.
An example of a typical transjugular single action biopsy device 20 is shown in FIGS. 1–3. Biopsy device 20 includes an outer hollow needle 22 defining a lumen 24 therethrough. An inner needle 26 is slidingly engaged inside lumen 24 and is moveable relative to outer needle 22. The inner needle 26 defines a first or distal end 28 having a tissue cutting point 30 and a cavity 32 adjacent first end 28 for receiving tissue samples. The inner needle 26 is slidable relative to outer needle 22 between a first retracted position (FIG. 3) and a second extended position (FIG. 2). In the first retracted position, inner needle 26 is retracted within lumen 22 so that outer needle 22 covers cavity 32 so that the distal end can be inserted into the liver. In the second extended position, the first end 28 of inner needle 26 is extended away from outer needle 22 to expose cavity 32 to tissues at the biopsy site. Such means are known in the art and commercially available. For example, biopsy devices of this type are available form U.S. Biopsy, Inc., a division of Promex, Inc., 3049 Hudson Street, Franklin, Ind., (317) 736-0128.
During a transjugular liver biopsy an elongated introducer 34, as illustrated in FIG. 4, is inserted through a small incision or puncture made in the skin. The introducer 34 is an elongated, small diameter cannula defining a lumen 36 that receives and guides the distal end 35 of biopsy device 20 to the biopsy site. A tip 38 of the introducer 34 is carefully advanced through venous passageways with the assistance of X-ray or fluoroscopy. Great care is taken to position the tip 38 at the precise location of the intended biopsy site. The biopsy device 20 is then advanced through the introducer lumen 36 and thereafter tissue cutting point 30 of inner needle 26 enters the liver tissue. During this insertion stage of the procedure, inner needle 26 is positioned within outer needle 22 in the first, retracted position (FIG. 3).
Once device 20 has been positioned at the targeted site for the biopsy, inner needle 26 is momentarily driven into liver tissue far enough to expose cavity 32 of inner needle 26. Liver tissue then prolapses into cavity 32. The device is then fired to advance outer needle 22 along inner needle 26 to cover cavity 32. This forward movement of outer needle 22 severs the prolapsed tissue to obtain a tissue sample, which becomes trapped in cavity 32 of inner needle 26. Movement of inner and outer needles 26, 22 to capture a sample occur almost instantaneously via firing mechanism 27 engaged with proximal ends 29 of needles 26, 22. The quality of the sample is largely dependent on the thrust or “strike” of outer needle 22 securing the tissue since the tissue is often parenchymatous tissue and is gelatinous in consistency. With outer needle 22 blocking the opening of cavity 32, biopsy assembly 20 may then be withdrawn, carefully backing out of introducer 34 leaving the introducer in place. Biopsy device 20 is then withdrawn from the target site carrying the sample within cavity 32. To collect the biopsy sample outer needle 22 is once again retracted to expose cavity 32 of inner needle 26. Typically, the biopsy device is re-inserted into the introducer to collect another biopsy sample. The procedure may be repeated several more times until satisfactory samples have been obtained.
A problem associated with this type of biopsy device is that the rigid inner and outer needles 26, 22 are metallic, commonly stainless steel, and lack the flexibility to freely move within the introducer 34 due to the significant curve 42 located at the introducer's distal end 44 (FIG. 4). The curve 42 of the introducer 34 causes the inner and outer needle 26, 22 to bind with an inner wall 46 comprising lumen 36 of the introducer 34, which in turn, can cause movement of the introducer. Consequently, the introducer is prone to movement due to the formation of resistance between inner and outer needles 26, 22 traversing curve 42 in introducer 34. Movement of the introducer once it is ideally placed is undesirable since damage to the surrounding tissue and poor biopsy samples are frequently the result of such movement. Moreover, since the curve 42 in the introducer causes continuous binding, even after the outer needle 22 has cleared the curve 42, much of the momentum imparted on inner and outer needles 26, 22 via spring force of firing mechanism 27 is utilized to overcome this binding or frictional force. Consequently, the effectiveness of the firing mechanism 27 is diminished resulting in recovery of small and fractured tissue specimens. Moreover, repeatedly firing the biopsy device 20 during subsequent sampling events causes the sliding surfaces of the outer needle 22 and inner wall 46 of introducer 34 to become “galled” i.e., deformation of the sliding surfaces, resulting in an additional and significant decrease in performance of the firing mechanism 27. As a result, little if any tissue is recovered and the device 20 may be permanently damaged before an adequate specimen is captured. The damaged device is then discarded and additional devices must then be used to capture adequate and sufficient tissue. This is unfortunately common and leads to a significant and unwarranted cost increase due to equipment, personnel and room charges, as well as an extended biopsy procedure for the patient.
Biopsy of an organ deep within the body, such as the liver, requires the introducer tip to be implanted a significant dept. Since the quality of the specimen is largely dependent on the striking momentum of the biopsy device over this long distance, a large degree of stiffness of the needles is necessary to transmit striking force from the firing device to the tip of the coring needles. Unfortunately, the needles tend to bind with the lumen walls of the long introducer at the bend. Thus, what is needed is a needle assembly that provides flexibility without compromising the stiffness and integrity of the needles.
U.S. Pat. No. 4,907,598 to Bauer discloses an alternative to rigid inner and outer needle assemblies by employing a flexible cannula and wire assembly that flexes as the curve in the introducer is traversed. The wire, comprised of a cable, and the cannula, provided with a stacked coil arrangement are designed to enhance flexibility. Problematically, the flexible cable and cannula assembly are generally flaccid in disposition providing a biopsy tip, located at the distal end of the cable and cannula assembly, that is unwieldily and uncontrollable. Moreover, a significant amount of energy of the firing device is lost by the flexible cannula and wire assembly as it yields when the firing device is activated. Consequently, small and fragmented specimens are captured and multiple additional firings are generally required.
U.S. Pat. No. 5,620,415 to Lucey et al. discloses a surgical device constructed to transmit forces applied at a handpiece through a bend region of a rigid outer tube. Force is transmitted from the handpiece to a cutting tool through a pair of internested tubes supported within the rigid tube. The assembly provides a flexible region caused by the inner tube having a series of circumferential slots that lie completely within the bend region at the time the handpiece is operated. In addition, the circumferential slots are parallel to each other and extend from opposite sides of the inner tube to form an accordion-like design. These circumferential slots provide a limited measure of binding relief at the bend, however an unsatisfactory level of relief for deep internal organ biopsy. In addition, these slots result in a loss of axial strength, and ultimately, a loss in precision between the stationary tube and the inner movable tube. As an added disadvantage, it is very expensive to produce the accordion-like design of these slots.
U.S. Pat. No. 5,911,701 to Miller and Ireland discloses a surgical cutting instrument having a curved outer cannula which slidably supports a cutting member disposed therein. The cutting member is attached to a continuous tubular member consisting of a rigid portion affixed to a flexible body portion extending along the curve of the outer cannula. To ensure a propitious measure of axial rigidity in the flexible body portion a plurality of driving cables are provided within the flexible body portion. Although the device is flexible, it is a motorized surgical cutting device, and the degree of complexity introduced by the concept is not desirable in the single and double action biopsy devices used for intravascular accessed biopsy procedures.
A need has remained for a transjugular biopsy device that overcomes the resultant binding force imparted by the introducer on the needle coring assembly. Additionally, what is needed is a transjugular biopsy device amenable to repeated uses without a measurable degradation in performance. Further, an inexpensive biopsy device that may be repeatedly fired without damage to the device would be desirable.